The recent publicity and emphasis on the "information superhighway" has increased awareness and acceptance of the Internet as a mass communication media. This broad based recognition of the Internet as a viable media for communication and interaction across multiple networks has also created a large established user base built upon the Internet standardized protocols for interaction between computer networks.
The paradigm for the Internet is that of a client-server relationship where Internet clients (browsers) communicate with Internet servers. To provide greater access to the Internet the communication protocols and languages utilized by the clients and servers have become standardized. These protocols include the Hyper-Text Transfer Protocol (HTTP), which is the communication protocol used for communications between clients and servers, and the Transfer Control Protocol/Internet Protocol (TCP/IP) the TCP portion of which is the transport specific protocol for communication between computers or applications. Also standardized is the language in which clients and servers communicate which is called Hyper-Text Markup Language (HTML). Because these protocols and language are machine independent, and utilize a connectionless best-efforts protocol to sending information, each transaction is fully self contained. Thus, for example, each message from a client contains information about the capabilities of the browser and is independent of any other communications for the communication to be completed. This self-contained nature of the communications between a client and a server may be referred to as "stateless" communications and increases the amount of data which must be transferred between a client and a server for a given communication.
In the context of the World Wide Web client/server applications the client may be a web browser which acts as the user interface. The web browser sends user requests to the appropriate web server and formats and displays the HTML data returned from the web server. The web browser also evaluates the HTML data to determine if there are any embedded hyper-link statements in the HTML data which would require subsequent browser requests which would then be initiated by the browser. A web server acts as the server for the client and processes the web browsers requests and returns the requested response as an HTML data portion of a HTTP data stream.
As an example of a typical world wide web communication the case of a web browser initiating a request for a "home page" from the web server illustrates the basic relationship between HTTP, HTML, TCP and the web browser and server. When the user of the web browser requests information from a specific web site, the web browser initiates communication with the web server by sending a "get" request to the web server specifying the Universal Resource Locator (URL) of the desired web site which, for purposes of this example, may be a "home page." The URL acts as the address of the web site and is unique throughout the Internet. The web server would then obtain and supply the web browser with the HTML data corresponding to the home page specified by the URL. This operation may involve further communications on the Internet by the Internet web server or the URL may specify the server which is in the local network to which the browser is attached. The web browser would then evaluate the HTML data received as an HTTP data stream from the web server to see if there were any embedded hyper-links such as an icon or an image and, if such a hyper-link exists would initiate requests specifying the URL of the hyper-link to obtain the specified data. This data would then be incorporated into the home page and displayed to the user. As is seen in this simple example, a single user input request by a web browser may result in multiple additional requests which are automatically carried out by the web browser in response to the receipt of the HTML data corresponding to the user input request.
The basic communication structure for an Internet based system is depicted in FIG. 1. In FIG. 1 a web browser 10 communicates with a web server 20 over a communication link 15. This communication link is typically a local area network connection, wide area network connection, a connection over telephone lines or a combination thereof. The web browser 10 communicates with the web server 20 using TCP/IP. For the majority of Internet communications a web browser communicates with a web server using the generic communication protocol HTTP which is transmitted between the web browser and the web server over the TCP/IP link between the web browser and the web server. The actual data transferred between the web browser 10 and the web server 20 are HTTP data objects (e.g. HTML data) as described above. The web server 20 may be a proxy which receives web browser communications from a number of web browsers and routes them to the appropriate server.
The popularity of the web browser/web server and their common information and transport protocols, HTML and HTTP, has lead to rapid acceptance of web technology as a universal interface for network access to information. Furthermore, because the protocols and language for communication between web browsers and web servers are standardized the communication protocols and language will be the same whether a user is using Netscape Navigator.TM., NCSA Mosaic.TM., WebExplorer.TM. or any other web browser as their web browser to access network information. Therefore, the large installed user base for web browsers combined with the connectivity of the Internet and the ease of writing web application servers using the HTTP defined Common Gateway Interface (CGI)make web technology very attractive for a large class of forms-based applications.
At the same time that the Internet was growing in popularity and acceptance, mobile computing was also increasing in popularity. The use of laptops, notebooks, Personal Digital/Communication Assistants (PDAs/PCAs) and other portable devices has lead to an increase in demands for wireless communications. Wireless wide area networks, cellular communications and packet radio, however, suffer from common limitations if used in a web context. The high cost per byte of communications, slow response time, low bandwidth and unreliability all hamper use of wireless technology for the stateless communication protocol of the World Wide Web. Also, because the web protocol is stateless the amount of data per request and the number of communication requests transferred over the wireless connection are larger than would be necessary if the communication were not self contained. Thus, combining wireless technology, or any low-speed communication technology, with web technology seems impractical as the strength of the web technology in its universal nature exacerbates the weaknesses of the wireless technology.
In addition to the disadvantages of using wireless communications in the web client/server environment, traditional caching techniques are also only of limited use. Refreshing cached data received from a web server presents reliability and availability difficulties when used in the web environment. For example, if cached data is refreshed each time a new instance of a web browser is initiated then a number of unnecessary browser request may be generated if the information is not utilized during the particular instance of the web browser. If cached data is not refreshed then the data in the cache may not be reliable.